package servlet;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 *
 * @author wjxing
 *
 */
public class MD5 {
    /**
     * 使用md5的算法进行加密
     */
    public static String md5(String plainText) {
        byte[] secretBytes = null;
        try {
            secretBytes = MessageDigest.getInstance("md5").digest(
                    plainText.getBytes());
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("没有md5这个算法！");
        }
        String md5code = new BigInteger(1, secretBytes).toString(16);// 16进制数字
        // 如果生成数字未满32位，需要前面补0
        for (int i = 0; i < 32 - md5code.length(); i++) {
            md5code = "0" + md5code;
        }
        return md5code;
    }

    /**
     * 可逆的的加密解密方法；两次是解密，一次是加密
     * @param inStr
     * @return
     */
    public static String convertMD5(String inStr){

        char[] a = inStr.toCharArray();
        for (int i = 0; i < a.length; i++){
            a[i] = (char) (a[i] ^ 't');
        }
        String s = new String(a);
        return s;

    }

    /*public static void main(String[] args) {
        String s = md5("1234");
        System.out.println("MD5后："+s);
        System.out.println("MD5后再加密："+convertMD5(s));
        System.out.println("MD5加密后解密："+convertMD5(convertMD5(s)));
        String s2 = convertMD5("12345");
        System.out.println("可逆的加密解密方法之加密："+s2);
        System.out.println("可逆的加密解密方法之解密："+convertMD5(s2));
    }*/



}
